Identification of lithium-sulfur battery discharge products through super(6)Li and super(33)S solid-state MAS and super(7)Li solution NMR spectroscopy

• Published in: Surface science Vol. 631; pp. 295 - 300
• Main Authors: Huff, Laura A, Rapp, Jennifer L, Baughman, Jessi A, Rinaldi, Peter L, Gewirth, Andrew A
• Format: Journal Article
• Language: English
• Published: 01.01.2015
• Subjects: Cathodes; Discharge; Electric batteries; Lithium; Lithium sulfur batteries; NMR spectroscopy; Nuclear magnetic resonance; Polysulfides; Spectra
• ISSN: 0039-6028
• DOI: 10.1016/j.susc.2014.06.028

super(6)Li and super(33)S solid-state magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy was used to identify the discharge products in lithium-sulfur (Li-S) battery cathodes. Cathodes were stopped at different potentials throughout battery discharge and measured ex-situ to obtain chemical shifts and T sub(2) relaxation rates of the products formed. The chemical shifts in the spectra of both super(6)Li and super(33)S NMR demonstrate that long-chain, soluble lithium polysulfide species formed at the beginning of discharge are indistinguishable from each other (similar chemical shifts), while short-chain, insoluble polysulfide species that form at the end of discharge (presumably Li sub(2)S sub(2) and Li sub(2)S) have a different chemical shift, thus distinguishing them from the soluble long-chain products. T sub(2) relaxation measurements of discharged cathodes were also performed which resulted in two groupings of T sub(2) rates that follow a trend and support the previous conclusions that long-chain polysulfide species are converted to shorter chain species during discharge. Through the complementary techniques of 1-D super(6)Li and super(33)S solid-state MAS NMR spectroscopy, solution super(7)Li and super(1)H NMR spectroscopy, and T sub(2) relaxation rate measurements, structural information about the discharge products of Li-S batteries is obtained.